24: All systems go

We have been funded on Kickstarter, which is great! It will be another couple of weeks before any money shows up in the business accounts so in the mean time I can be doing a load of admin.

I will be migrating this blog from wordpress.com to wordpress.org over the next couple of days. Theoretically everything should remain the same, but I expect there will be a few hours of downtime so don’t be alarmed if you try to get on and it’s dead. The main reason for this is so that it gives me a little more autonomy over the site, since I am going to need all sorts of things like pre-order forms, extra pages, on site videos, proper email addresses etc.

For those who haven’t been to the Kickstarter page, the rough action plan is as follows:

Step 1 – Get PCB v0.4 ordered.
This PCB has 3 main difference over v0.3. Firstly, there is no external HDMI input, instead the video feed comes directly from the Raspberry Pi’s GPIO headers in the form of DPI. While v0.3 had a Pi mounted on it by the end, it fed its video via an HDMI cable fed back into the board. The second major difference is some big old slots cut in the PCB. I held off incorporating them before in case they resulted in significant loss of structural integrity (not something you want in a PCB spinning at 900 rpm, and especially not in one you can’t afford to replace). Fingers crossed this one won’t fail, but if it does, it’s a failure that has been budgeted for. The final main difference is that the frame synchronisation will now be governed by a hall effect sensor, rather than by roughly matching the rotation speed to the frame rate of the HDMI source (which is what resulted in the god awful line synchronisation issue which is really really obvious about a minute into the video). v0.3 was actually capable of this, but due to lack of time and slip ring data channels it never got implemented. Doing so will mark the last major revision of the VHDL.

A few other tweaks will include getting rid of the ridiculous 1 meter latch signal trace that for some bizarre reason didn’t seem like a problem at the time, making sure that the PCB is insulated from the shaft (ground loops seemed to play absolute havoc with the USB and HDMI), and switching to a slightly friendlier voltage regulator (the last one I used required about 20 different valued resistor and capacitors). The PCB design is ready to go, so all I need is the money to arrive and then I can submit it for fabrication.

Step 2 – Organise a load of admin and design related things.Logos, a more professional website, a proper Github account, software licenses, some graphic design work etc. While most of this is not urgent it would be nice to get some of this stuff underway early.

Step 3 – Decide which workshop space I will use.
I recently looked round a great maker space called Makerversity, based in Somerset house in central London. It has a good vibe, lots of start-ups, small businesses and other creative types all working alongside each other.

The other option is to work out of the University of Kent at Canterbury, where I have been based for the last 8 years while I did my bachelor’s and PhD. Our mechanical workshop is pretty well kitted out and it would be very easy for me to simply continue working from there.

I’ll let you all know exactly where I end up. If any of you ever end up there then you will of course be welcome to come and have a look behind the scenes, and grab a drink.

Step 4 – Prototype new mechanical design.
The latest PCB will replace v0.3 in the prototype, since its mechanical housing is already in place and working. This will allow me to start working on the new code as soon as possible as well as identify any further problems that will need to be ironed out in V0.5.

The next step will be to create a new prototype of the mechanical side of things, which will require almost a complete redesign. I still haven’t got round to weighing the first version, but I wouldn’t be surprised if it was close to 40KG, mainly due to the steel frame, top, bottom and rear plates, cast iron bearing flanges and squirrel cage 3 phase motor.

We will be switching over to a BLDC motor, a shorter, aluminium frame, replacing the steel plates with either aluminium or composite and a host of other improvements with the aim of cutting manufacturing costs and simplifying the assembly process.

Step 5 – Software and smartphone apps.
The core software that will run on the Raspberry Pi will be open source. More than likely I will end up doing the majority of this myself. The plan is to expand and incorporate some existing open source software, such as Xplanet and EarthWindMap to allow a variety of planetary and meteorological data to be displayed, as well as some additional content.

The smartphone apps will probably be contracted out, once I have the specification for interfacing with the main app. If I have time I may do it myself, but budget has been set aside for having it done externally if need be.

Step 6 – Design and prototype PCB v0.5.
This PCB will not be a huge change over 0.4. The main differences being switching over from a Pi Zero W to a Compute Module (or similar). For those who aren’t familiar, the Compute Module is an almost completely broken out Raspberry Pi with a SODIMM connector and are the preferred device for those who want to use a Pi for a commercial purpose. It provides a couple of bonuses over the Pi Zero. Due to the fact that basically every peripheral is broken out (USB, HDMI etc.) we can A. potentially switch back to using HDMI from DPI (reducing noise and potentially freeing up some IOs on the FPGA) and B. Dispense with the USB through slip rings and instead program our FPGA directly from our Pi. This will in turn allow us to reclaim the space at the bottom of the PCB where the cables went, allowing us to increase our resolution up from the 240 of the prototype, up to 256.

In some ways it would make sense to jump straight to this design, skipping v0.4. However, because the Pi Compute is fairly different from the Pi Zero W, I will need to prototype a smaller PCB first to verify things like a Wifi module, voltage regulators, the direct HDMI to FPGA interface etc. which would take additional time, and I really want to get Globe out of storage and back into action ASAP.

Step 7 – Test the damn thing actually lasts and complies with regulations.
Once we have our new mechanical housing and PCB, we should be ready to start testing. I aim to delivery you a really reliable, solid device, and that means it needs to be capable of operating for several hours, every day, for a prolonged period of time. The major things I will be looking at will be the slip rings, bearings and motors. I will be looking to develop 5 or so of these devices, which will also allow me to illustrate the different cladding options. These test units (assuming I haven’t tested them to failure by then) can then serve as demonstration units.

Step 8 – Order the components and build.
By this point I should have ironed out any final kinks in the design, producing any additional PCB and mechanical prototypes as required. This leaves the main task of ordering all the individual components: PCBs, slip rings, power supplies, motors etc. (most of which are coming from China) and once they arrive, assemble, test and package all of your wonderful whirly Globes.